混杂设备

混杂设备与字符设备的关系：
 混杂设备是字符设备的一种，混杂设备把一些不好归类的字符设备驱动归为混杂类，舍弃了普通字符设备的注册方式，结构更简单。
 
混杂设备驱动：
 1、调用模块初始化函数注册misc设备（注册misc结构体）
  模块初始化函数：static int __init name(void)
  调用：module_init(name);
  注册函数原形：int misc_register(struct miscdevice * misc)
  
 2、创建模块卸载函数
  模块卸载函数：static void __exit name(void)
  调用：    module_exit(name);
  卸载函数原形：int misc_deregister(struct miscdevice *misc)
  
 3、调用声明：MODULE_LICENSE("GPL");
 
 4、创建misc结构体，填充其结构体成员，如下：
  static struct miscdevice misc = {
   .minor = MISC_DYNAMIC_MINOR,
   .name = DEVICE_NAME,
   .fops = &dev_fops,
  };
  
  name 是misc设备驱动的名字
  fops成员是字符设备操作文件结构体，因此下一步我们需要完成该结构体
  
  misc设备操作结构体原型:
   struct miscdevice  {
    int minor;
    const char *name;
    const struct file_operations *fops;
    struct list_head list;
    struct device *parent;
    struct device *this_device;
    const char *nodename;
    umode_t mode;
   };
  
 5、创建普通字符设备操作文件结构体，并填充其结构体成员
  static struct file_operations dev_fops = {
   .owner  = THIS_MODULE,
   .ioctl  =  name_ioctl,
   .open    =   name_open,
   .read    =   name_read,
   .write   =   name_write,
   .poll    =   name_poll,
   .release =   name_release,
  };
  
  字符设备操作文件结构体原型：
   struct file_operations {
    struct module *owner;
    loff_t (*llseek) (struct file *, loff_t, int);
    ssize_t (*read) (struct file *, char __user *, size_t, loff_t *);
    ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *);
    ssize_t (*aio_read) (struct kiocb *, const struct iovec *, unsigned long, loff_t);
    ssize_t (*aio_write) (struct kiocb *, const struct iovec *, unsigned long, loff_t);
    int (*readdir) (struct file *, void *, filldir_t);
    unsigned int (*poll) (struct file *, struct poll_table_struct *);
    long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long);
    long (*compat_ioctl) (struct file *, unsigned int, unsigned long);
    int (*mmap) (struct file *, struct vm_area_struct *);
    int (*open) (struct inode *, struct file *);
    int (*flush) (struct file *, fl_owner_t id);
    int (*release) (struct inode *, struct file *);
    int (*fsync) (struct file *, loff_t, loff_t, int datasync);
    int (*aio_fsync) (struct kiocb *, int datasync);
    int (*fasync) (int, struct file *, int);
    int (*lock) (struct file *, int, struct file_lock *);
    ssize_t (*sendpage) (struct file *, struct page *, int, size_t, loff_t *, int);
    unsigned long (*get_unmapped_area)(struct file *, unsigned long, unsigned long, unsigned long, unsigned long);
    int (*check_flags)(int);
    int (*flock) (struct file *, int, struct file_lock *);
    ssize_t (*splice_write)(struct pipe_inode_info *, struct file *, loff_t *, size_t, unsigned int);
    ssize_t (*splice_read)(struct file *, loff_t *, struct pipe_inode_info *, size_t, unsigned int);
    int (*setlease)(struct file *, long, struct file_lock **);
    long (*fallocate)(struct file *file, int mode, loff_t offset,
        loff_t len);
   };

 6、对普通字符设备操作文件结构体的操作成员一一完成其函数,直接从file_operations的成员调用相应原型函数即可